<template>
  <ul class="list">
    <li class="item" @touchstart="handleTouchStart" 
    :ref="item"
    @touchmove="handleTouchMove"
     @touchend="handleTouchEnd" v-for="item of letters"
      :key="item" @click="handleLetterClick">{{item}}</li>
  </ul>
</template>

<script>
  export default {
    name: 'CityAlphabet',
    props: {
      cities: Object
    },
    data(){
return{
    touchStatus:false
}
    },
    computed:{
        letters(){
            const letters = []
            for(let i in this.cities){
                letters.push(i)
            }
            return letters
        }
    },
    methods: {
      handleLetterClick(e) {
        this.$emit('change', e.target.innerText)
        // console.log(e.target.innerText)
      },
      handleTouchStart() {
        this.touchStatus = true
      },
      handleTouchMove(e) {
if(this.touchStatus){
const startY = this.$refs['A'][0].offsetTop
const touchY = e.touches[0].clientY - 79
const index = Math.floor((touchY - startY)/20)
if(index >= 0 && index<this.letters.length){
this.$emit('change',this.letters[index])
}
}
      },
      handleTouchEnd() {
        this.touchStatus = false

      },
    }
  }

</script>

<style scoped>
  .list {
    display: flex;
    flex-direction: column;
    justify-content: center;
    position: absolute;
    right: 0;
    top: 1.58rem;
    bottom: 0;
    width: 0.4rem;
  }

  .item {
    line-height: 0.4rem;
    text-align: center;
    color: #00bcd4;
  }

</style>
